in (your) birthday suit

humorous

not wearing any clothes.

He walked out of the bathroom in his birthday suit - obviously not expecting to find anyone in the flat.

• bail out
• bail out of
• bail out of something
• bail someone out
• baker's dozen
• balancing act
• ball and chain
• ball-breaker
• ball is in court
• ball is in someone's court
• ball is in your court
• balloon goes up
• ballpark estimate
• ballpark figure
• balls-up
• banana republic
• banana skin
• Band-Aid
• bandwagon effect
• bandy about
• bandy something about
• bane of life
• bane of your life
• bang away
• bang for buck